1. Field of the Invention
This invention relates to a dual-mode bandpass filter with at least two adjacent cavities being mounted in a planar relationship to one another.
2. Description of the Prior Art
It is known to have a dual-mode bandpass filter with each cavity being mounted in an axial relationship to one another and containing a dielectric resonator. This type of filter is described in Institute of Electrical and Electronics Engineers Transaction on Microwave Theory and Techniques, Vol. MTT-30, No. 9, September, 1982, pages 1311-1316, by S. J. Fiedziuszko. A filter with axially mounted cavities has some disadvantages in that the cavities must be manufactured within a narrow tolerance as the dimensions of each cavity are critical. This makes the cavity relatively expensive to manufacture. Also, axially mounted cavities are more difficult to mount on a channel or can only be tuned over a relatively narrow range.
It is an object of the present invention to provide a bandpass filter having adjacent cavities that are mounted in a planar relationship relative to one another, contain a dielectric resonator and are versatile in that they can be tuned over a relatively broad range.